Image forming apparatuses are used as printers, facsimile machines, copiers, plotters, or multi-functional devices having two or more of the foregoing capabilities. As one type of image forming apparatus employing a liquid-ejection recording method, for example, an inkjet recording apparatus is known that uses a recording head serving as a liquid ejection head (liquid-droplet ejection head) to eject droplets of ink. During image formation, such liquid-ejection-type image forming apparatuses eject droplets of ink or other liquid from the recording head onto a recording medium to form a desired image.
Such liquid-ejection-type image forming apparatuses fall into two main types: a serial-type image forming apparatus that forms an image by ejecting droplets from the recording head while moving the recording head in a main scanning direction of the carriage, and a line-head-type image forming apparatus that forms an image by ejecting droplets from a linear-shaped recording head held stationary in the image forming apparatus.
The liquid ejection head has, for example, nozzles to eject liquid droplets, individual pressure chambers (also referred to as pressurizing chambers, ejection rooms, and liquid channels) communicating the nozzles, pressure generation units (energy generation units) to generate pressure (energy) for pressurizing liquid within the pressure chambers, and common chambers of a relatively large volume to supply liquid to the pressure chambers. Pressure generated by the pressure generation units pressurizes liquid within the pressure chamber to eject liquid droplets from the nozzles.
The pressure generation units are, for example, thermal actuators that generate film boiling of liquid (ink) by electro-thermal transducers, such as heat-generation resistant, to cause a phase change, piezoelectric actuators employing, e.g., piezoelectric elements (used as a synonym for electro-thermal transducers in this disclosure), or electrostatic actuators that generate pressure by electrostatic force.
For the liquid ejection head, it is necessary to raise the internal pressure of the individual pressure chambers to eject liquid droplets. The pressure generated at this stage causes liquid droplets to be ejected from the nozzles and, at the same time, is transmitted to the common chambers. The pressure may be transmitted back to the individual chambers, thus causing unexpected fluctuations in the internal pressure of the individual pressure chambers. Such fluctuations hamper droplet ejection at a desired speed and amount, thus causing ejection failure. In particular, in a case in which a plurality of individual pressure chambers is simultaneously pressurized to eject liquid droplets, the pressure transmitted from the individual pressure chambers to the common chambers becomes relatively great, which tends to cause ejection failure. In addition, if the fluctuations in pressure transmitted to the common chambers are transmitted to adjacent pressure chambers to affect liquid in the pressure chambers, that is, mutual interference occurs, leak or ejection of liquid droplets from unintended nozzles or unstable ejection state may be caused. As a result, outputting high quality images may be hampered.
In particular, in a case in which the driving frequency of pressure generation units is raised to increase image formation speed and image quality, such reflection of the pressure transmitted from the individual pressure chambers to the common chambers may cause complex behavior of pressure in the pressure chambers, thus hampering accurate ejection of liquid droplets. Alternatively, in a case in which an increased number of nozzles are used, the shape of the common chambers may be tapered toward end portions in the longitudinal direction of the common chambers. In such a case, at the longitudinal end portions of the common chambers, pressure fluctuates relatively greatly, thus giving more influence to the individual pressure chambers than a longitudinal middle portion of the common chambers. As a result, a difference in the behavior of pressure may occur between positions of the individual pressure chambers in the nozzle array direction, thus hampering proper control of the behavior of pressure.
Therefore, it is preferable to minimize such fluctuations in the internal pressure of the common chambers and the difference in the behavior of pressure between positions of the individual pressure chambers in the nozzle array direction.
Hence, conventionally, a damper may be disposed to absorb or minimize fluctuations in the internal pressure of the common chambers. However, because a damper formation member formed of a thin film material is quite thin to perform the function as a damper, it is difficult to retain the damper formation member by itself. Hence, conventionally, a thin film member and a substrate for supporting the thin film member may be integrated and machined so as to leave the thin film member in a damper portion. For example, JP-2001-353871-A and JP-2006-347036-A propose to use a clad member in which a thin film member is bonded to a plate member, etch the plate member to form a damper chamber, and use the thin film member as a damper.
However, as described in JP-2001-353871-A and JP-2006-347036-A, in a case in which the clad member in which the thin film member is bonded to the plate member is used, glue for bonding the thin film member to the plate member remains on the thin film member. Such residual glue increases the hardness of a portion of the thin film member that acts as the damper or causes deformation due to a difference in coefficient of linear expansion between the thin film member and the glue, thus hampering proper damper performance of the thin film member.